The art of punching sheets of paper for assembly into booklets or binders is highly developed.
Examples in the prior art include Glaeser patent U.S. Pat. No. 1,739,572, granted Dec. 10, 1929 in which a pair of holes or three holes can be punched into a sheet or plurality of sheets by manually depressing cylindrical punches, which are spring loaded to an upward position, to force the punches into a die plate so as to form punched holes in the paper.
Particularly, in recent years, with the advent of sheet post processing devices which are employed in association with printers and copiers for feeding sheets of paper serially to form sets of paper, it has become the practice to include automatic means for punching the sheet with two or more holes, as the sheet is moved into the post processing unit from the printer or copier.
Such a post processing machine, for example, is shown in Muramatu et al patent U.S. Pat. No. 4,988,030 granted Jan. 29, 1991 wherein a photocopying machine supplies sheets which are punched and stapled before delivery to a paper receiving tray.
Shigemura et al patent U.S. Pat. No. 5,253,030 granted Oct. 12, 1993 shows another form of apparatus as the sheets are post processed. As disclosed in this patent, a number of punches are arranged transversely of the sheet path between a plate which defines a guide for the punches and a second plate which defines a die for each of the punches. The punches are cam actuated and individually spring loaded to an upper position. Also in this construction, the punch actuating cams are mounted upon a common shaft and sequentially cause the punches to be driven through the paper and into the respective die holes thereby delaying the timing of the punching action of the punches to relieve the load on the drive system.
Various other punching systems are known enabling the sheet to be punched on the fly between opposed rotary dies and punches, by moving the punch assembly along with the sheet or by temporarily halting movement of the sheet in the punch assembly.